浙江三门湾沉积记录：U k37表层海水温度和浮游植物群落变化与El Niño/La Niña的关联

摘要

Historical sea surface temperature (SST) record during the past~180 years was reconstructed using the unsaturation index of long-chain Alkenones (Uk37) in the sediment sampled from the Sanmen Bay. Simultaneously, changes of single-diatom, single-dinoflagellate and single-coccolithophores were recovered using three biomarkers, brassicasterol, dinoflagellate sterol and long-chain Alkenones. The results show that the reconstructed SST varies between 15.19~17.61 ℃, which is closed to the observation SST values in fall, and its secular trend is consistent with the global warming. The SST fluctuation may be related to the El Niño/La Niña oscillations. The gross primary productivities range from 710.7 to 6 998.5 ng/g and also show upward trend in the past 180 years. The most abundant phytoplankton in the sediment is diatom and the secondary dinoflagellate. Diatom/Dinoflagellate ratio fluctuated in the range of 2.6~7.2, which indicate sensitivity of the coastal phytoplankton in response to the changes in the marine environment. The abundance of phytoplankton cell and the community structure can be dramatically influenced by El Niño events, when the abundance of phytoplankton cell increases, but the number of the species and population diversity decrease significantly. As no regular seasonal pattern in the change of the abundance of phytoplankton cell, we conclude that the El Niño condition should be the primary influcencing factor to that change.%　　应用三门湾沉积柱样中长链烯酮不饱和指数（U k37）与表层海水温度SST的关系重建历史上的El Niño/La Niña事件；利用3种浮游植物标志物菜子甾醇（brassicasterol）、甲藻甾醇（dinosterol）和长链烯酮C37（alkenones）来恢复单一种硅藻Diatom、甲藻Dinoflagellates和颗石藻Emiliania huxleyi变化。研究结果表明：（1）U k37估算温度在15.19～17.61℃波动，与当地秋季海水实测温度接近。U k37估算的温度清晰地再现了全球变暖的趋势，且其波动可能与El Niño/La Niña震荡有关。（2）浮游植物标志物总含量变化范围为710.7~6998.5 ng·g-1，180年以来呈总体上升趋势。沉积记录中硅藻相对比例最高、甲藻次之，硅藻/甲藻比值在2.1~7.2波动，表现出近岸浮游植物对海洋环境变化的敏感性。（3）El Niño/La Niña事件可影响到浮游植物细胞丰度以及群落结构变化，在El Niño盛期，浮游植物细胞丰度剧增，而浮游植物种类数及群集多样性程度明显减少。另外，浮游植物细胞丰度的季节性规律不明显，El Niño事件可能是影响三门湾海域浮游植物生产力的主要因素。